"use client";

import { useQuery } from "@tanstack/react-query";
import type { ScheduleSlot } from "@/app/(main)/tv/components";
import type { ScheduledSlotResponse } from "@/lib/types";

// ---------------------------------------------------------------------------
// Pure transformation utilities
// ---------------------------------------------------------------------------

/** Format an ISO-8601 string to "HH:MM" in the user's local timezone. */
export function fmtTime(iso: string): string {
  return new Date(iso).toLocaleTimeString([], {
    hour: "2-digit",
    minute: "2-digit",
    hour12: false,
  });
}

/** Progress percentage through a slot based on wall-clock time. */
export function calcProgress(startAt: string, durationSecs: number): number {
  if (durationSecs <= 0) return 0;
  const elapsedSecs = (Date.now() - new Date(startAt).getTime()) / 1000;
  return Math.min(100, Math.max(0, Math.round((elapsedSecs / durationSecs) * 100)));
}

/**
 * Seconds elapsed since a slot started, computed from the current wall clock.
 * Use this instead of `broadcast.offset_secs` when the broadcast may be cached —
 * start_at is a fixed timestamp so the offset is always accurate regardless of
 * when the broadcast response was fetched.
 */
export function calcOffsetSecs(startAt: string): number {
  return Math.max(0, (Date.now() - new Date(startAt).getTime()) / 1000);
}

/** Minutes until a future timestamp (rounded, minimum 0). */
export function minutesUntil(iso: string): number {
  return Math.max(0, Math.round((new Date(iso).getTime() - Date.now()) / 60_000));
}

/**
 * Map EPG slots to the shape expected by ScheduleOverlay.
 * Marks the slot matching currentSlotId as current.
 */
export function toScheduleSlots(
  slots: ScheduledSlotResponse[],
  currentSlotId?: string,
): ScheduleSlot[] {
  return slots.map((slot) => ({
    id: slot.id,
    title: slot.item.title,
    startTime: fmtTime(slot.start_at),
    endTime: fmtTime(slot.end_at),
    isCurrent: slot.id === currentSlotId,
  }));
}

/**
 * Find the slot immediately after the current one.
 * Returns null if current slot is last or not found.
 */
export function findNextSlot(
  slots: ScheduledSlotResponse[],
  currentSlotId?: string,
): ScheduledSlotResponse | null {
  if (!currentSlotId || slots.length === 0) return null;
  const idx = slots.findIndex((s) => s.id === currentSlotId);
  if (idx === -1 || idx === slots.length - 1) return null;
  return slots[idx + 1];
}

// ---------------------------------------------------------------------------
// useStreamUrl — resolves the 307 stream redirect via a Next.js API route
// ---------------------------------------------------------------------------

/**
 * Resolves the live stream URL for a channel, starting at the correct
 * broadcast offset so refresh doesn't replay from the beginning.
 *
 * The backend's GET /channels/:id/stream endpoint returns a 307 redirect to
 * the Jellyfin stream URL. Since browsers can't read redirect Location headers
 * from fetch(), we proxy through /api/stream/[channelId] (a Next.js route that
 * runs server-side) and return the final URL as JSON.
 *
 * slotId is included in the query key so the URL is re-fetched automatically
 * when the current item changes (the next scheduled item starts playing).
 * Within the same slot, the URL stays stable — no mid-item restarts.
 *
 * Returns null when the channel is in a gap (no-signal / 204).
 */
/**
 * Resolves the stream URL for the current slot, with StartTimeTicks set so
 * Jellyfin begins transcoding at the correct broadcast offset.
 *
 * slotId is in the query key: the URL refetches when the item changes (new
 * slot), but stays stable while the same slot is playing — no mid-item
 * restarts. offsetSecs is captured once when the query first runs for a
 * given slot, so 30-second broadcast refetches don't disturb playback.
 */
export function useStreamUrl(
  channelId: string | undefined,
  token: string | null,
  slotId: string | undefined,
) {
  return useQuery({
    queryKey: ["stream-url", channelId, slotId],
    queryFn: async (): Promise<string | null> => {
      const params = new URLSearchParams();
      if (token) params.set("token", token);
      const res = await fetch(`/api/stream/${channelId}?${params}`, {
        cache: "no-store",
      });
      if (res.status === 204) return null;
      if (!res.ok) throw new Error(`Stream resolve failed: ${res.status}`);
      const { url } = await res.json();
      return url as string;
    },
    enabled: !!channelId && !!slotId,
    staleTime: Infinity,
    retry: false,
  });
}